The goals of this supplemental application remain the same as those outlined in our initial application. Those objectives as originally stated in June of 1976 are reproduced here. This study is directed toward the identification of avian sarcoma virus (ASV)-coded non-virion proteins. Antiserum from mammalian hosts which carry ASV-induced tumors will be used to identify virus-specific and transformation-specific antigens in ASV-infected chick cells. To date we have obtained hamster antiserum which will specifically immune precipitate 35S-methionine-labeled antigens form ASV-transformed chick cells which correspond to virion internal group-specific antigens and their precursors, plus antigens not previously reported in infected cells. Antiserum will be produced in several other species in order to ensure the greatest variety of immunological responses. These studies will be extended using ASV-transformation defective and temperature sensitive mutant-infected chick cells in order to identify those antigens that are transformation-specific. If such a protein(s) is identified, it will be purified and its intracellular location determined. In this way, we hope to deduce how such a protein(s) functions. Now that the product of the ASV src gene has been identified, the major emphasis in our laboratory has shifted to its purification and studies on its mechanism of action. However, many ofthe original experiments proposed are still incomplete. We will utilize: 1) immunoprecipitation techniques, 2) enzymatic and nonenzymatic degradation in order to characterize proteins, 3) ion-exchange and immunoaffinity chromatography, and 4) protein kinase assays.